CORN 1ST THE GREAT PLAINS AREA. 



In these investigations seasonal variations in climatic factors have 

 been of more importance in crop production than differences in 

 methods of tillage. This is shown by the fact that at some stations 

 in some years climatic conditions have been such that all methods have 

 resulted in practical failures in yields. In other years all methods 

 have given fair returns. 



Figure 2 shows the earliest and latest dates of the last killing frost 

 in the spring, the earliest and latest dates of the first killing frost in the 

 fall, and the average length of the frost-free period at each station. 

 The heavy hatched horizontal bars represent the periods between the 

 average dates of the last killing frost in the spring and the first killing 

 frost in the fall, or the average frost-free period, the actual number of 

 days being also shown. The solid-line curve at the left shows the 

 earliest date at which the frost-free period has begun. The broken- 



o o s & S"o & * 



JULY 



& P. 



JUDITH BASIN 



HUNTLEY 



MLLISTON 



DICKINSON 



EDGELEY 



HETTINGER 



BELLEFOUPCHE 



SCOTTSBLUFF 



NORTH PLATTE 



AKROAf 



HAYS' 



GARDEN CITY 



OALHART 



AMARILLQ 



t)\tilijai»i\(\iHis$ i 



Fig. 2. — Diagram showing the average frost-tree periods and the earliest and the latest dates at which 

 the last killing frost in the spring and the first killing frost in the fall has occurred at fourteen stations 

 in the Great Plains area. 



line curve at the left represents the latest date at which the last killing 

 frost of the spring has occurred. The solid-line curve at the right 

 represents the earliest date and the broken-line curve at the right the 

 latest date at which the first killing frost of the fall has occurred. 



This diagram shows clearly the increase in the length of the frost- 

 free period from the north to the south. The shortest average frost- 

 free period is 100 days at Hettinger and the longest one 194 days at 

 Amarillo. The length of the period free from frost is more important 

 in the production of corn than in the production of the small grains. 

 Young corn being easily injured by frost, planting must be delayed 

 until there is little further danger from this source. Where the 

 season is short the crop may be caught by frost in the fall. This 

 necessitates the use of short-season varieties in a portion of the Great 

 Plains. As a season of average length can not be depended on, the 



